1. Field of the Invention
The present invention relates to the production of multi-metal powders by electro-deposition techniques.
2. Description of the Prior Art
An expanding area of technological innovation of diverse application is that of powder metallurgy. Metal compositions and forms can be obtained by pressure molding fine metal powders or mixtures of powders into a desired shape. The pressed object may then be heated, in an atmosphere which protects the metal against oxidation, at a temperature at which the crystals of the metal powder grains grow and regrow into each other across the powder grain boundaries without melting. In this fashion, the metallic crystalline equivalent of conventional production by casting and machining is produced. Powder metallurgy methods are especially favorable and desirable where one is concerned with conserving energy and materials as well as avoiding the waste and losses which attend the usual conventional melting, casting, rolling, and machining used to produce metal machinery components.
Powder metallurgy, in the past twenty-five years, has become an advanced science and has generated considerable amounts of applied technology. Metal powders with uniform chemical and physical characteristics are becoming available, making possible the production of high quality powder metallurgy products. The growth of the field is predicated upon basic economic and technological advantages which are inherent in powder metallurgy products and the processes for making them. This is particularly so when one considers the flexibility and versatility which is introduced in the integration of powder metal alloys.
Essentially, conventional powder metal products are formed by the compression molding of a suitable powder into a desired shape and then consolidating the same by a mild heat treatment. This type of production saves both direct machining costs as well as those indirect energy and waste losses normally associated with the salvage and reprocessing of machine shop and original foundry process scrap. In the present and future eras of intensifying shortages of energy and materials, these advantages of powder metallurgy methods are of fundamental importance to our economy and commerce.
Most conventional articles fabricated by powder metallurgy are multi-component or alloyed as opposed to a product comprised of a single metal component. This is because of the multitude of properties such as tensile strength, hardness, flexibility, etc., which are required for the performance characteristics of a variety of end products. Conventional powder metallurgy produced alloy articles are made from powders of the available alloy, or from an admixture of powders of the separate alloy components. Available methods for the reduction of an alloy to a powder, such as attrition or atomization, are not free of those factors which degrade the powder's chemical purity, especially that which exists at the surface.
Furthermore, these conventional methods do produce waste which is most often unsalvageable, and also consume excessive amounts of fuel. Moreover, the equipment is frequently complex and optimized to accommodate a particular material. Against this backdrop of prior art and attendant problems, applicant has developed various electrolytic methods for the production of high density copper powder as described in his co-pending Application Ser. No. 539,771, filed Jan. 9, 1975, now U.S. Pat. No. 3,994,785, issued Nov. 30, 1976. Therein copper powder of lower apparent density is used as a cathode for the formation of copper powder having a desired relatively high apparent density by means of an integral two-phase process.
The prior art is also aware of such processes as those described in U.S. Pat. No. 3,832,156 to Wilson et al which converts low green strength spherical metal powders to high green strength particles by physically changing the particle shape. In the Wilson et al patent the atomized powders are ball-milled into flakes which are annealed above the recrystallization temperature in a non-oxidizing atmosphere. The resultant sintered cake is then mechanically disintegrated into irregularly shaped particles. Although related to the field of interest, this process is basically very different from applicant's invention which employs various electro-deposition techniques. Additionally, the Wilson et al process appears to be much more time consuming and difficult to control for an economic yield.
Also representative of the prior art is U.S. Pat. No. 3,838,982 which issued Oct. 11, 1974 to Sanderow et al, wherein the various powder metal particles are coated with a different metal having a melting temperature lower than that of the metal of the particles themselves. In Sanderow et al the coating metal fills the voids between the particles so that the object is impervious to fluids.
In view of this aforementioned technology, applicant has identified and examined the described problem areas, and extended his basic discoveries relating to the production of copper powder by electro-deposition into new methods of value for producing integral alloy powder metallurgy particles.